dumb
The title screen is awesome.
I think using some photos/pics works OK - specially the earth. if you want to appeal to more folk though, I'd suggest taking more time over the backgrounds. Maybe take out the black lines and put in more detail. And redraw the characters with more detail.
Gohan slamming into the ground was pretty funny
The sound was quality
Goku's dialogue was just dumb - his first line after seeing his brother just makes him sound like an idiot and the 2nd line makes no sense.
Try putting dialogue and text in boxes or at least choose your fonts and colours a bit more judiciously. Using verdana just seems wrong in such a violent flash. Maybe even use a bitmapped font?
There are good elements here, but overall I felt underwhelmed by the whole thing.